1. Field of the Invention
The present invention relates to an electronic camera, or more particularly, an electronic camera capable of illuminating an object with a strobe.
2. Description of the Related Art
Generally, for a silver-film camera and electronic camera, when the luminance of an object is insufficient or any intention works on photography, a strobe or the like is usually used to irradiate illumination light for photography. At this time, an amount of flash emitted from the strobe is controlled by various means. According to a conventionally adopted means, an amount of flash is detected using, for example, a light adjustment device. When the amount of flash has reached a predetermined value, flashing is stopped.
The location of the light adjustment device in a camera varies depending on a design or appearance. For example, the light adjustment device sometimes is included as an optical system independent of a photographic optical system outside the photographic optical system. However, when a camera having the light adjustment device as the independent optical system is put to use, a range of exposure and a range of photometry may be mismatched in some photographic situations, or especially, during close photography. Consequently, an exposure error is likely to occur. This is a well-known phenomenon.
Single-lens reflex camera users request accurate exposure. For preventing the mismatch between the range of exposure and range of photometry, it is preferred to measure a beam having passed through a photographic optical system so as to control an amount of flash for stroboscopic photography.
In a conventional silver-film type single-lens reflex camera, a strobe light adjustment device is located on the bottom of a mirror box. Reflected light from the film passing through a photographic optical system is detected, and an amount of flash emitted from a strobe is controlled correspondingly. This technology is well known.
For the electronic camera, a CCD is used as an imaging device. A light receiving window of the CCD is made from a transparent glass. It is therefore impossible to utilize light reflected from an imaging surface of a silver film. In the electronic camera, therefore, a beam passing through a photographic optical system is used to detect an amount of strobe light in efforts to remove influence of a parallax. Moreover, a light adjustment device is realized with the imaging device. For stroboscopic photography, a strobe is flashed preliminarily. An amount of preliminary flash is detected by the imaging device. An amount of strobe light required for actual flashing is determined based on the results of detection. Photography is then carried out. This so-called preliminary flashing method is widely adopted.
However, the preliminary flashing method proves effective only when a built-in strobe of an electronic camera is used. When a multi-strobe mode is adopted, since an external strobe must be flashed synchronously with the built-in strobe, the electronic camera cannot accommodate the use of the external strobe. According to the preliminary flashing method, the strobe cannot be accurately controlled to flash a certain small amount of light. An exposure error is therefore likely to occur during close photography.
According to another technology that does not utilize reflection from a film, a photographic optical system and a viewfinder optical system share components, and a light adjustment device is included in the viewfinder optical system. For example, Japanese Unexamined Patent Publication No. 9-166817 has disclosed a single-lens reflex camera. In the single-lens reflex camera, a pop-up full reflection mirror is located on an optical path in the photographic optical system, and light reflected from the full reflection mirror is routed to the viewfinder optical system. The signal-lens reflex camera includes a diffusion plate located in an optical path in the viewfinder optical system, and a light adjustment device for detecting light diffused by the diffusion plate. For photography, preliminary flashing is performed with the full reflection mirror located in the optical path in the photographic optical system. An amount of strobe light is detected by the light adjustment device. An amount of strobe light required for actual flashing is determined based on the results of detection. The full reflection mirror is withdrawn from the optical path in the photographic optical system. Actual flashing is then performed for photography.
For the camera described in the Japanese Unexamined Patent Publication No. 9-166817, a conceivable means for controlling an amount of strobe light will be described below. Specifically, the pop-up full reflection mirror included in a single-lens reflex optical system is replaced with a translucent reflection mirror. An amount of flashlight emitted during photography is detected in real time in order to control an amount of strobe light. However, a beam passing through the photographic optical system must be split into light incident on the imaging device and light incident on the viewfinder optical system. The light incident on the viewfinder optical system must be split into light incident on an eyepiece and light incident on the light adjustment device. This results in an insufficient amount of light. In particular, an amount of light routed to the viewfinder optical system is smaller than that routed to the imaging device. When the small amount of light is distributed to the light adjustment device, a viewfinder image observed through the eyepiece appears dark.
An object of the present invention is to provide an electronic camera capable of accurately detecting an amount of strobe light according to a beam passing through a photographic optical system, and of preventing a view observed through a viewfinder from appearing dark.
Briefly, according to the present invention, there is provided an electronic camera including a strobe, a single-lens reflex optical system, a light adjustment device and an optical path switching means. The strobe is used to illuminate an object. The single-lens reflex optical system consists of a photographic optical system and a viewfinder optical system. The photographic optical system converges an incident beam reflecting from the object on an imaging device to form an image thereon. The viewfinder optical system routes at least part of the beam having passed through the photographic optical system to an eyepiece so that the object can be observed through the eyepiece. The light adjustment device detects an amount of light emitted from the strobe and reflected from the object. The optical path switching means is included in the viewfinder optical system, and routes a beam reflected from the object selectively to the eyepiece and light adjustment device.
The object and advantages of the present invention will be further apparent from the following detailed explanation.